1. Field of the Invention
The present invention relates to hearing aids. The invention more specifically relates to hearing aids having a wireless transceiver with improved transmission range. The invention also relates to a method of fitting a hearing aid comprising a wireless transceiver.
In the context of the present disclosure, a hearing aid should be understood as a small, microelectronic device designed to be worn behind or in a human ear of a hearing-impaired user. A hearing aid system may be monaural and comprise only one hearing aid or be binaural and comprise two hearing aids. Prior to use, the hearing aid is adjusted by a hearing aid fitter according to a prescription. The prescription is based on a hearing test, resulting in a so-called audiogram, of the performance of the hearing-impaired user's unaided hearing. The prescription is developed to reach a setting where the hearing aid will alleviate a hearing loss by amplifying sound at frequencies in those parts of the audible frequency range where the user suffers a hearing deficit. A hearing aid comprises one or more microphones, a microelectronic circuit comprising a signal processor, and an acoustic output transducer. The signal processor is preferably a digital signal processor. The hearing aid is enclosed in a casing suitable for fitting behind or in a human ear.
As the name suggests, Behind-The-Ear (BTE) hearing aids are worn behind the ear. To be more precise, an electronics unit comprising a housing containing the major electronics parts thereof is worn behind the ear. An earpiece for emitting sound to the hearing aid user is worn in the ear, e.g. in the concha or the ear canal. In a traditional BTE hearing aid, a sound tube is used to convey sound from the output transducer, which in hearing aid terminology is normally referred to as the receiver, located in the housing of the electronics unit and to the ear canal. In some modern types of hearing aids a conducting member comprising electrical conductors conveys an electric signal from the housing and to the receiver placed in the earpiece in the ear. Such hearing aids are commonly referred to as Receiver-In-The-Ear (RITE) hearing aids. In a specific type of RITE hearing aids the receiver is placed inside the ear canal. This is known as Receiver-In-Canal (RIC) hearing aids.
In-The-Ear (ITE) hearing aids are designed for arrangement in the ear, normally in the funnel-shaped outer part of the ear canal. In a specific type of ITE hearing aids the hearing aid is placed substantially inside the ear canal. This type is known as Completely-In-Canal (CIC) hearing aids. This type of hearing aid requires an especially compact design in order to allow it to be arranged in the ear canal, while accommodating the components necessary for operation of the hearing aid.
In some hearing aid types a wireless link is provided between the two hearing aids of a binaural hearing aid system. In this case an inductive wireless link is particularly advantageous because the power consumption can be very low over such small distances. Further, since the hearing aids of the binaural hearing aid system are adapted to be worn in or at a left and right ear of a hearing aid user, it is advantageous to employ an inductive wireless link because the magnetic field signals transmitted by the inductive wireless link are not significantly attenuated by the head of the hearing aid user.
In yet other types of hearing aids an inductive radio is used to wirelessly communicate with external signal sources or external relay devices, such as a hearing aid remote control or a hearing aid fitting system. In this type of hearing aids the external signal source or the external relay device must be within close range because the transmission range of the inductive radio falls off approximately with the distance raised to the third power and because the availability of electrical power and supply voltage is generally limited in a hearing aid.
2. The Prior Art
EP-B1-1688016 discloses a transceiver for a hearing aid. The transceiver has a trimming capacitor and a coupling capacitor that are implemented as off-chip components.
Generally, off-chip capacitors are advantageous in that they can sustain a higher voltage than on-chip components and disadvantageous with respect to size and cost. Especially it is relatively expensive to trim the off-chip capacitors since this requires use of external equipment such as e.g. a laser. Trimming of the capacitors is generally required in order to compensate deviations of the inductance of the inductive antenna from the nominal value.
In order to further optimize the transceiver performance it is advantageous that the resonance frequency of the transceiver is constant independent on whether the transceiver is transmitting or receiving. Generally, this puts rather strict requirements on the relative dependencies of the capacitance values of the trimming capacitor, coupling capacitor and the input capacitance of the Low Noise Amplifier (LNA) of the wireless transceiver, requirements that can be difficult to meet in practical implementations with the consequence of decreased transceiver performance and consequently higher power consumption if the requirements are not fulfilled.
It has been proposed in the art to use trimming capacitors that can be trimmed digitally, but these are limited in the voltage they can sustain.
It is a feature of the present invention to provide a hearing aid with an improved wireless transceiver, hereby providing a hearing aid with a long wireless transmission range while maintaining a hearing aid that provides relatively inexpensive manufacturing costs and the possibility of adjustment of the resonance circuit of the wireless transceiver during normal operation and without requiring the use of external equipment.
It is still another feature of the present invention to provide an improved method for fitting a hearing aid comprising a wireless transceiver.